Update app.py

app.py

@@ -47,7 +47,7 @@ def generate_math_solution_openrouter(api_key, problem_text, history=None):
         messages.append({"role": "user", "content": f"Solve this math problem step-by-step: {problem_text}"})  ## Solve this math problem step-by-step: {what is 2+2?}
 
         completion=client.chat.completions.create(
-            model="minimax/minimax-m2:free",
+            model="meta-llama/llama-3.3-70b-instruct:free",
             messages=messages,
             extra_headers={
                 "HTTP-Referer": "https://advancedmathtutor.edu",